Image producing apparatus

ABSTRACT

A copy of an image is produced by utilizing the temperature dependency of the magnetic permeability of a magnetizable material in a device which comprises a cylindrical wall having a horizontal axis and formed with an inner cavity. Along the outer periphery of the cylindrical wall are formed a plurality of closely spaced grooves extending in longitudinal direction of the cylindrical wall. The cylindrical wall is rotatable about its axis and a feeding arrangement is provided for introducing magnetizable pulverulent material such as a magnetic ink into the grooves at a portion of the outer periphery of the cylindrical wall which is upstream of the top portion of the rotating wall. Means are provided for passing concurrent with the rotation of the cylindrical wall an image-carrying sheet along the top portion thereof and for passing a carrier sheet for the image to be formed along the bottom portion of the cylindrical wall, so that when the cylindrical wall serves as a printing cylinder the carrier sheet passes the cylinder in a printing plane and contacts the cylinder along a printing line formed by the lowermost portion of the cylinder. A heating arrange ment is so located as to heat the image-carrying sheet in the area of contact of the same with the outer surface of the cylindrical wall so that the magnetizable material in the grooves located in this area of contact will be selectively heated according to a pattern corresponding to the image, thereby forming in the magnetizable material in the grooves a selective pattern of predetermined magnetic permeability corresponding to the image. A source of magnetic force is located in the cavity of the cylinder adjacent to the portion of the cylindrical wall which passes from the area of contact with the image towards the printing line, and serves for holding in the grooves only the portions of the magnetic pulverulent material which forms the selective pattern of predetermined permeability, whereas the other portions of the pulverulent material are allowed to fall off the cylinder. The source of magnetic force is so arranged that the magnetic force will terminate adjacent but spaced from the radial plane of the cylindrical wall passing through the printing line, whereby at the printing line the pulverulent material forming the selective pattern will no longer be subjected to magnetic force and will drop from the grooves onto the carrier sheet forming thereon a copy of the image.

United States Patent Germany [21 Appl. No. 804,956 [22] Filed Mar. 6,1969 Division of Ser. No. 428,964, Jan. 29, 1965, Patent No. 3,472,695.

[45] Patented Mar. 2, 1971 [32] Priority Feb. 6, 1964 [3 3] Germany [54]IMAGE PRODUCING APPARATUS 10 Claims, 10 Drawing Figs.

[52] U.S.Cl 101/150, 346/74,1l7/l7.5,101/468,101/132,101/471, 118/637[51] Int. Cl B41m 1/10, B41f 9/00 [50] Field of Search 346/74;117/17.5;l01/(ESD),150, 132,468,471; 118/637 4 [56] References CitedUNITED STATES PATENTS 3,126,492 3/1964 Swoboda 346/74X 3,250,636 5/1966Wilferth l17/17.5 3,279,367 10/1966 Brown 346/74X 3,301,948 1/1967 Todt346/74X 3,343,174 9/1967 Kornei l 346/74 3,364,496 l/l968 Greiner et a1346/74 3,472,695 10/1969 Kaufer et al. 117/17.5X 3,496,304 2/1970 Nelson346/74X Primary ExaminerEdgar S. Burr Attorney Michael S. StrikerABSTRACT: A copy of an image is produced by utilizing the temperaturedependency of the magnetic permeability of a magnetizable material in adevice which comprises a cylindrical wall having a horizontal axis andformed with an inner cavity. Along the outer periphery of thecylindrical wall are formed a plurality of closely spaced groovesextending in longitudinal direction of the cylindrical wall. Thecylindrical wall is rotatable about its axis and a feeding arrangementis provided for introducing magnetizable pulverulent material such as amagnetic ink into the grooves at a portion of the outer periphery of thecylindrical wall which is upstream of the top portion of the rotatingwall. Means are provided for passing concurrent with the rotation of thecylindrical wall an imagecarrying sheet along the top portion thereofand for passing a carrier sheet for the image to be formed along thebottom portion of the cylindrical wall, so that when the cylindricalwall serves as a printing cylinder the carrier sheet passes the cylinderin a printing plane and contacts the cylinder along a printing lineformed by the lowermost portion of the cylinder. A heating arrange mentis so located as to heat the image-carrying sheet in the area of contactof the same with the outer surface of the cylindrical wall so that themagnetizable material in the grooves located in this area of contactwill be selectively heated according to a pattern corresponding to theimage, thereby forming in the magnetizable material in the grooves aselective pattern of predetermined magnetic permeability correspondingto the image. A source of magnetic force is located in the cavity of thecylinder adjacent to the portion of the cylindrical wall which passesfrom the area of contact with the image towards the printing line, andserves for holding in the grooves only the portions of the magneticpulverulent material which forms the selective pattern of predeterminedpermeability, whereas the other portions of the pulverulent material areallowed to fall off the cylinder. The source of magnetic force is soarranged that the magnetic force will terminate adjacent but spaced fromthe radial plane of the cylindrical wall passing through the printingline, whereby at the printing line the pulverulent material forming theselective pattern will no longer be subjected to magnetic force and willdrop from the grooves onto the carrier sheet forming thereon a copy ofthe image.

Ptented March 2,1971 3,566,786

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Patented March 2,1971 3,566,786

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HELMUT KAUFER y ERICH BURGER HANS-PETER HUBER Patented March 2, 1971 4Sheets-Sheet 4.

INVENTOR.

HELMUT KAUFER ERICH BURGER By HANS-PETER HUBER AYN/(l/ ff/rrln IMAGEPRODUCINGAPPARATUS CROSS-REFERENCES TO RELATED APPLICATIONS The presentapplication is a division of our copending application Ser. No. 428,964,filed Jan. 29, 1965, now Pat. No. 3,472,645, and entitled Method andApparatus for Forming an Image.

BACKGROUND OF THE INVENTION The present invention relates to anapparatus for forming an image and, more particularly, the presentinvention is concerned. with forming a visible image with the help of amagnetizable material, by heating the magnetizable material in a patterncorresponding to the image to be formed and by utilizing the-variationof a magnetic property of the magnetizable material as a function of thetemperature for producing a latent magnet image.

Several methods have been proposed for making latent magnet imagesvisible and for magnetically. transferring the same onto a suitableimage carrier. Such magnet printing processes are easy to carry outbecause the printing process itself as well as the possibly requiredcleaning steps can be carried out with the help of suitable magneticfields without direct contact, whereby the intensity of the magnetfields can be easily controlled. When a graduated latent magnet imagehas been produced or is available, it is even possible to producehalftone prints thereof.

However, up to now, these advantages were connected with thedisadvantage that the latent magnet image could be produced only in arelatively involved and difficult manner. According to the knownmethods, for instance, the latent magnetic image is produced bypointwise magnetizing a permanently magnetizable layer, whereby theenergizing current of the electromagnet is controlled through aphotocell amplifier which scans an image which is to be reproduced. Inanother device which may be used for rapid printout in connection withelectronic data processing apparatus, a matrix which'is formed of smallmagnet coils is activated corresponding to the image so as to form amagnetic replica thereof. Another method of the prior art proposes theforming of'a magnetic printing form by application of a highly permeablematerial in accordance with the pattern of the image to be produced.

Whenever in the present specification and claims reference is made topermeability, this is to denote magnetic permeability.

It has also been attempted toproduce a latent magnetic image by heatinga portion of a premagnetized layer of magnetic material, which portioncorresponds to the image which is to be reproduced, above the Curiepoint of the material. Thereby, however, the useful range oftemperatures is extremely limited by the coercive forces. Even whenusing the most favorable magnetic material which presently is availablefor this process, such-as ferromagnetic chromium oxides, it will befound that for Curie points in the temperature range which is suitablefor the forming of an image or an image copy by application of heat, thecoercive force drops to the lower limit of the value which is suitablefor magnetic image formation and copying. Even at the upper limit of thetemperature range which is suitable for the heat copying method, thecoercive forces which can be brought to play suffice only fortheselective attraction of very easily movable pigment particles which arelocated at a very small distance from the magnetic layer.

lt is therefore an object of the present invention to provide anapparatus which will overcome the above discussed difficulties anddisadvantages.

It is another object of the present invention to provide a device forforming an image or an image copy by utilizing the temperaturedependency of the magnetic permeability of a magnetizable material,which device may be operated in a simple and economical manner.

SUMMARY or THE INVENTION A device for forming a copy of an image byutilizing the temperature dependency of the magnetic permeability of amagnetizable material is proposed according to thepresent invention,which device comprises a cylindrical wall having a.

substantially horizontal axis, defining an inner cavity and formed atits outer surface with a plurality of closely spaced cal wall animage-carrying sheet along the top portion-0f the;

same, and a carrier sheet for the image to be formed along the. bottomportion of the cylindrical wall sothat when the cylindrical wall servesas a printing cylinder, the carrier sheet passes the cylinder in aprinting plane and contacts the cylinder along a printing line formed bythe lowermost portion of the cylinder, heating means for heating saidimage carrying,

sheet in the area of contact of the same with the outer surface of thecylinder so that the magnetizable material in the grooves located in thearea of contact will be selectively heated according to a patterncorresponding to the image thereby forming in the magnetizable materialin the grooves a selective pattern of predetermined magneticpermeability corresponding to the image, magnetic means located in thecavity of the cylindrical wall adjacent the portion of the cylindricalwall passing from the area towards the printing line for holding in thegrooves only the portion of the magnetic pulverulent material formingthe selective pattern of predetermined permeability while allowing theother portions of the pulverulent material to fall of the cylindricalwall, the magnetic means terminating adjacent to but spaced from theradial plane of the cylindrical wall passing through said printing line,whereby at" the printing line said pulverulent material forming theselective pattern will no longer be subjected to the magnetic force ofthe magnetic means and will drop from the grooves onto said carriersheet forming thereon a copy of the image.

Preferably, the cylindrical wall is formed of translucent material oflow heat conductivity and the grooves are so shaped as to define a scoopwheel-shaped configuration at the outer periphery of the .cylindricalwall.

The heating means'maybe located outside the cylindrical wall or withinthe inner cavity defined by the cylindrical wall. The magnetic meanspreferably include. a curved, permanently magnetic plate locatedinwardly of and closely adjacent to the portion of the cylindrical wallwhich passes from the heating means to the printing line and, accordingto a preferred embodiment of the present invention, the-device alsoincludes fixing means for fixing the. image-forming pulverulent materialto the carrier sheet. If the pulverulent material includes a low meltingcomponent, the fixing means will preferably include second heating meansfor melting the low-melting component on the carriersheet and therebyfixing the image-forming pulverulent material to the carrier sheet.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows the permeability curves ofseveral materials. which are suitable for producing a transitory, latentmagnetic.

image, as a function of the temperature;

FIG. 2 shows a schematic arrangement for the forming of a transitory,latent magnetic image in an intermediate layer;

FIG. 3 shows an arrangement wherein the transitory, latent" magneticimage is produced in a carrier layer for'the image forming magneticmaterial (ink);

FIG. 4 shows the forming of a transitory, latent image in a magnetizableink layer;

FIG. 5 is a schematic showing of the forming of a latent magnetic imagein a permanently magnetizable layer by means of an intermediate layer oftemperature-dependent permeability which is inserted as a variable,magnetic resistance into the magnetizing or demagnetizing field;

FIG. 6 shows a raster or screen of highly coercive andtemperature-dependent permeable, magnetizable material arranged in amagnetic field;

,FIG. 7 is a schematic illustration of the forming of a copy by using apermanently magnetizable magnetic ink;

.FIG. 8 illustrates schematically the use of a magnetizable sieve forapplying a soft magnetic ink;

FIG. 9 schematically illustrates theuse of a permanently magnetizableink carrier layer; and

FIG. 10 is an elevational cross-sectional view through a magneticcopying device wherein on a transfer cylinder a magnetic pulverulentimage is formed which may then be transferred to any desired backingsheet. A

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventionencompasses in a device for forming a copy of an image by utilizing thetemperature dependency of the magnetic permeability of a magnetizablematerial, in combination, means for forming a surface of magnetizablematerial, the permeability of which depends upon the heating of thematerial, means for selectively heating the surface according to apredetermined pattern so as to form within the surface a selectivepattern of surface portions within a predetermined range of permeabilitycorresponding to the selective patternof heating of the surface, andmeans for forming from the selective pattern of surface portions withinthe predetermined permeability a permanent reproduction having the samepattern.

Thus, according to the present invention, the magnetic image is producedwith the help of variations of the permeability as a function of thetemperature. A transitory, latent magnetic image is formed which issuitable for use in magnetic duplication processes as wellas forcarrying out a very effective printing process. For this purposemagnetizable materials are available in all temperature ranges includingalso the range of elevated temperatures directly adjacent to ambient ornormal room temperature. Thereby, the permeability may drop within arange of a few degrees centigrade from a four digit value to that of acompletely nonmagnetic material. Consequently, by utilizing relativelysmall heat differences, it is possible to selectively use externalmagnetic fields of any desired strength. Since the temperature dependentchange of the permeability is reversible, it is possible to store thematerials which are used for a certain specific manner of carrying outthe method of the present invention even at temperatures which are abovethe working temperature of the respective method.

A permanent latent magnetic image with, forpractical purposes, anydesired strength of permanent magnetic force can be produced in anyrange of working temperature provided that, as further proposedaccording to the present invention, a layer of temperature-dependentvariable permeability is introduced as a variable magnetic resistance ina magnetizing or demagnetizing field which penetrates a permanentlymagnetizable layer. The magnetic record may then be fixed in a highlycoercive magnetic material which may possess a Curie point which isconsiderably higher than the working temperature of the method, inother'words, the magnetic record may then form a latent image inpractically any presently known hard or permanently magnetic material.The layer of temperature-depending variable permeability which controlsthe intensity of the recorded signal need not by itself possess anypermanent magnetizability. Such materials are available in all desiredtemperature ranges.

Since the distribution laws which are valid for electric resistancesarranged in parallel are also applicable for the magnetic resistance oftwo adjacent portions of a layer which is permeated by a magnetic field,the magnetic fluxes through two adjacent portions or points of a layerwhich is located in an initially homogeneous magnetic field will behaveinversely to their local permeability number. Since further thematerials which are available for this method possess four digitpermeability values which upon heating to above the Curie temperaturewill drop to the value 1 of a nonmagnetic material, it is possible inthis manner to achieve very strong differences in the magnetization ofthe permanent magnetizable material which is located in the same or anyidentical magnetic flux. Depending on whether a permanent field or analternating field with decreasing amplitude is present, it is alsopossible to produce either a positive or negative image.

Very thin and easily heatable layers and a particularly low influence ofconstant magnetic resistance portions are obtained by exposing a networkformed of permanently magnetizable materials of low permeability andmaterials of high, temperature-dependent variable permeability to amagnetizing or demagnetizing field. 1

The present invention may be carried out by utilizing the increase inthe permeability which is connected with an increase in the temperatureparticularly of a ferrite or a mixed ferrite, or'the steep drop of thepermeability particularly of such materials in the vicinity of the Curiepoint for producing variations of magnetization according to the image.Particularly the last-mentioned effect is suitable for carrying out amethod which works very reliably and gives a great contrast, because inthis area of the permeability curve, i.e., in the vicinity of the Curiepoint, a temperature rise of a'few-degrees centigrade will convert themagnetizable material from its condition of maximum permeability into acompletely nonmagnetic condition of maximum permeability into acompletely nonmagnetic condition.

According to a further characteristic of the invention, it is possibleto produce a graduated latent magnetic image by utilizing theprogressive decrease of the permeability, particularly of a metallicmagnetic'alloy, for instance an iron-nickel alloy. When a graduatedmagnetic image which is obtained by means of a gradual increase ordecrease of the permeability coacts, for instance with a powderdispersion or emulsion ink layer in which the magnetizable pigmentparticles are slowed down dependent on the printing speed, then amagnetic halftone print is obtained. Depending on whether the increaseor decrease of the permeability is used, either a negative or a positivecopy of the original image is obtained.

Basically, the heat image which is required for producing the latentmagnetic image can be. applied in any desired manner, for instance byimpressing for a short period of time a heated die. However, for quickconversion of an original image which, for instance, is drawn orimprinted on'paper, into a latent magnetic image, preferably, the heatimage which is required for producing the latent magnetic image isproduced by an image controlled heat radiation. The known methods forproducing a heat image provide the utilization of reflected as well asof transmitted radiation. With both methods, i.e. with reflected as wellas with transmitted radiation, depending on the type of heat contactwith the original image, and depending on the length of radiation,positive or negative heat images may be produced. Further more, it isalso possible to apply the heat image by an optical copying system whichmay be based on projection through a transparency, or

also on projection of light reflected from an opaque image. In each ofthese reversible radiation methods, it is thus possible to adjust theentire copying method so as to obtain the most desirable positive ornegative effect with respect to the prevailing magnetic or copyingcondition.

In connection with the present magnetic copying method, particularlyfavorable conditions are achieved according to a further embodiment ofthe present invention by contacting an original image with a layer ofmagnetizable material which is interrupted by a translucent screen orraster, whereby the image-forming portions of the original image possessan ability point steeply dropping permeability characteristics, whichheat image comprises portions formed at a temperature closely below thetemperature at which the permeability reaches its maximum, as well asportions formed at a temperature which is above the Curie point.

When using transitory, latent magnetic images, according to a furthercharacteristic or embodiment of the present invention, an arrangementcan be made that a transitory or temporary, latent magnetic image isproduced in an intermediate layer which is arranged between an externalmagnetic pole and the backing for the image which is to be produced. Theimage-producing material will then be attracted under the influence of ahomogeneous magnetic field only at the portions of the backing sheet atwhich the heat image which has been formed in the intermediate layer hasleft a sufficient degree of permeability. Since, as described above, thepermeability can be changed by one to a thousand or can be brought froma four digit value to the value of a nonmagnetic material, it ispossible with this arrangement to achieve without difficulties a clearlydifferent actuation of the printing or image-forming and the nonprintingor nonimage-forming portions.

Particularly advantageous structural conditions are met when the latentmagnetic image is formed in a magnetizable carrier layer for the copy ofthe image which is to be formed or in a magnetically controlled sievefor the image-forming material. The image-forming material or magneticink will then be retained at the portions of the carrier layer in whichthe homogeneous magnetic field which acts on the magnetic ink and on thecarrier layer can produce large induced magnetic forces due to the stillhigh permeability at these portions. This is preferably the case whenthe permeability of the carrier layer is considerably greater than thepermeability of the magnetic ink and when the induction-causing magneticpole does not directly contact the magnetic ink. The printing magneticink is particularly firmly retained when it has to pass a regionallystrongly magnetically controllable sieve, somewhat comparable with thesilk screen process.

The simplest arrangement and at the same time the most immediate controlof the attraction of the magnetic ink by the heat image, without anyconversion loss is obtained when the latent magnetic image is producedin the image-forming or copy-forming material, for instance in alayer ofmagnetizable powder or in a magnetic ink layer. Here again, in thehomogeneous magnetic field only those particles of magnetic materialwill be attracted which still possess a sufficiently high degree ofpermeability. Thereby, negative or positive images may be produced byhaving the image formed either by the ink or magnetic powder portionwhich is thus transferred from the original layer thereof, or by the inkor magnetic powder portion of lower permeability which has not beenremoved from the layer and which may subsequently be fixed to itsoriginal support in suitable manner known in the art.

The term homogeneous magnetic field as used hereinabove is not meant todenote a field which shows no gradation but is to denote primarily afield which is homogeneous at its origin, in other words, which at itsorigin does not include portions of varying strength, for instancecorresponding to an image. It is entirely possible to produce a magneticfield which originates from two immediately adjacent magnetic poles andwhich is of diminishing strength in the direction towards theimage-forming layer, in other words, a magnetic field which in thestrict sense of the words would have to be considered an inhomogeneousmagnetic field, and to shift the same by means of an intermediate orcarrier layer of variable permeability in parts into the image-forminglayer.

The effect of the arrangement according to the present invention can befurther increased if the latent magnetic image is produced in aplurality of adjacent layers of magnetizable material which possesscomplementary magnetic properties.

Thus, for instance, a magnetic image may be produced in a carrier forthe magnetic ink as well as in the magnetic ink itself. If in such casethe permeability of the magnetic ink has characteristics opposite tothat of the carrier, then, at the heated portions, an intensifiedtransfer of the magnetic ink onto the carrier sheet for the copy whichis to be produced, or by reversal of the characteristics, an increasedadherence of the not or less heated portions of the magnetic ink attheir original support will be accomplished. The same holds also truefor the combination of magnetic ink and intermediate layer withidentical characteristics, and intermediate layer and support also withidentical characteristics, as well as basically also for the combinationof three layers, although in the latter case the exact application ofthe heat image becomes somewhat more difficult.

By utilizing the permanent latent magnetic image, it is possible toproduce the same according to a further embodiment in the presentinvention also in the image-forming material. For instance, it ispossible in a very simple manner by using an intermediate layer ofvariable permeability to accomplish a permanent magnetization of themagnetic ink corresponding to the image which is to be reproduced. Thetransfer of a thus prepared ink onto a carrier sheet can be achieved bythe simple expedient of placing underneath a highly permeable material,for instance a soft-iron plate.

A particularly effective separation of the printing and the nonprintingportions of the magnetic ink, i.e. of the imageforming portions of themagnetic ink from the remainder of the layer of magnetic ink can beachieved under utilization of the permanent latent magnetic image byusing a permanently magnetizable sieve for the image-forming materialsuch as a magnetic ink or magnetizable powder, which, for instance underinterposition of a variably permeable intermediate layer which has beenmagnetized or demagnetized in a pattern corresponding to the image whichis to be reproduced.

According to a further embodiment of the present invention, theimage-forming material may be applied onto a permanently magnetizablecarrier layer which contains the latent magnetic image, which carrierlayer has been premagnetized or demagnetized under interposition of avariably permeable intermediate layer. It is possible to operate withthe smooth surface of a thus produced printing form in a manner somewhatsimilar to the conventional litho printing. Due to the fact that theinking in, as well as the printing and the cleaning is carried outwithout direct contact, this method can be carried out in a muchsimplermanner than litho printing and the useful lifespan of the printing formis considerably prolonged.

Such permanently magnetizable carrier layer containing the latentmagnetic image is particularly suitable for attaching to a printingcylinder, whereby the printing form may be applied and extinguished inthe printing machine. This possibility may be utilized in a particularlyadvantageous manner in connection with the partial printing according tothe so-called system printing which is described for instance in U.S.Pat. No. 2,925,032.

It is also possible to form on a foil a layer which may be magnetizedcorresponding to an image and to attach the foil with the magnetizablelayer thereon onto a printing machine which may be provided with specialmagnetic ink supply and cleaning devices. Furthermore, such foil ofsynthetic material or paper on which an image has been formed byapplication of a magnetic pigment or magnetic ink may serve not only asprinting form but also as a copy of the original image by suitablyfixing the image-forming magnetic pigment or ink thereon.

Several methods are known for making the latent magnetic image visible.Preferably, according to a further embodiment of the present invention,the latent magnetic image is made visible by means of a magnetizablepowder with the individual particles thereof coated with a materialwhich will melt at a temperature abovethe working temperature requiredfor the forming of the magnetic image. In this case, the fixing of theimage formed of the magnetizable powder on a carrier sheet can becarried out in a very simple manner by heating above the workingtemperature to the melting temperature of the coating, whereby thismelting temperature may be sufficiently high so that the magnetizablepowder having such coating may be stored in the vicinity of room heatingdevices such as radiators or the like without endangering thestorability of the coated powder. This method is particularly suitablefor magnetic duplication processes.

According to another embodiment of the present invention, in a magneticprinting method, the latent magnetic image is to be made visible bymeans of a magnetic printing ink wherein in a known manner a proportionof magnetic pigment which is as high as possible is bound in a binderwhich will be taken up by paper. The large magnetic forces which can becontrolled according to the present invention permit application of themagnetic dye onto a carrier sheet without direct contact between themagnetic dye layer and the carrier sheet. Due to the absorbability ofthe binder in the carrier sheet, the printed sheets may be immediatelystacked so that the magnetic printing process can be carried out withthe same speed as conventional printing processes. 7

According to the present invention,'a device for carrying out the methodof the invention preferably should include at least a motor driventransporting roller, a source of heat radiation and an elongatedmagnetic bar such as is used for instance for extinguishing recordingson magnetic tapes. A particularly simple duplicating device is obtainedby providing a hollow cylinder which preferably carries at its outersurface a translucent screen or a plurality of closely adjacent groovesand which is contacted by a sheet carrying the original image, as wellas by a backing sheet for the copy which is to be produced. The cylinderserves as carrier for the image-form-' ing magnetizable material, whichis deposited in the grooves. Furthermore, a permanent magnet is providedwhich holds the portions of the magnetic powder, which serve for formingthe image, in the grooves while the cylinder surface rotates downwardly,so that the nonimage-forming portions of the pulverulent material willfall off the cylinder surface. The magnet is arranged so as to act onthe magnetizable powder between a heating area in which the same isheated corresponding to the image which is to be copied, and a transferarea or printing line in which the cylinder surface is preferablylocated directly above the backing sheet for the copy whichis to beproduced.

Furthermore, in a simple device according to the present invention forproducing undistorted, authentic copies, an endless resilient carrierband is provided which on its outer surface is formed with translucentgrooves and which passes through a bath of magnetic ink and a heatingzone, whereby the outer surface of the band serves as carrier for themagnetic ink which represents the image-forming material. Immediatelyfollowing the heating zone, in the direction of movement of the endlessband, a permanent magnet is provided which will draw the image-formingportions of the magnetic ink onto a carrier sheet which passes in thevicinity but out of contact with the endless band.

A device which permits the printing of a large number of copies as wellas the printing of single copies or system copies includes, according toa further embodiment of the present invention, a cylinder which carriesa permanently magnetizable carrier layer for the image-forming materialand around which a device for applying the heat image, a magnetizing ordemagnetizing device, a supply device for magnetic ink, a papertransporting device, a counter roller and a cleaning device arearranged. Preferably, there are also provided a pattern carriage forcarrying the original image which is to be copies or printed and whichcarriage will move with a speed corresponding to the circumferentialspeed of the cylinder, furthermore a mirror which can be interposed intothe path of the heat rays which form the heat image, as well as athermostatically controlled heating device for maintaining a cylindertemperature which is slightly below the working temperature of themethod. The ink supplying device, preferably, will include an inkcontainer having a permanently magnetized outlet opening or screenopening, the magnetic forces of which will permit the flowing out of themagnetizable ink only under the combined influence of the gravity actingon the magnetic ink and the magnetic force of the ink carrier layer.

The strong permanent magnetic image which which can be producedaccording to the present invention can be used in a particularlyadvantageous manner for carrying out magnetic printing by applying to acarrier layer which is permanently magnetized in accordance with theimage to be reproduced, a magnetizable material forming on the carrierlayer a relief corresponding to the magnetic image, and the raisedportions of which can be inked with conventional relief printing ink.Preferably, the surface of the carrier layer is provided with grooves orthe like, in order to prevent a dislocation of the relief image duringthe printing process.

Referring now to the drawing, and particularly to FIG. 1, the mixedferrites Ni Zn ,Ee o Ni ln Fe fl, and Mn, ,zn,, ,e,o, are taken from,treatise ,Ferrite by Dr. .1. Smit, Dr. H. P. P. J. Wijn, Philipstechnische Bibliothek 1962 The first two mentioned materials belong to asystem of materials within which the temperature-dependent properties ofthe materials can be continuously changed as a function of theproportion of Ni or Zn. 1500 N 4" is the trade name of a ferrite whichis obtainable from the firm Sienens and Halske AG for use in highfrequency cores. Thermoperm" is the trade name of an iron-nickel alloywhich is available for temperature compensation in magnetic loops andproduced by the firm Krupp.

If the ambient room temperature is indicated by A, the temperature atwhich the permeabilityreaches its maximum by D and the temperature atwhich the permeability of the material drops to the value 1 of anonmagnetic material, which temperature is substantially identical withthe Curie temperature, is indicated by C, it will be seen that heatingof the materials from A to BlB4 will cause an approximately linear riseof the permeability by a factor of about 1.5 in each case, which uponsuitable arrangement of the magnetic field and the retarding forces inthe binder containing the magnetic pigments may be used for producing amagnetic image. In the case of heating Thermoperms for A to C5, apermeability curve is found which drops by the factor with substantiallylinear gradation, which, for instance, is suitable for producingmagnetic halftone prints.

Particularly favorable conditions are obtained when the temperaturedifference between B and C is used for forming the magnetic image.Thereby heating by less than 5C. will cause a sudden change in thedegree of permeability by a factor of 1,000. With devices operating inthis range of permeability change, it is not necessary to takeparticular care with respect to the adjustment between the magneticfields and the retarding forces of the magnetic pigment. If the pigmentitself consists of a material which within the working temperature rangeof the method possesses a suddenly changing permeability, then thepigment will be attracted at the temperature B by very weak magneticfields, while upon exceeding temperature C, the pigment cannot be movedeven by the strongest magnetic fields because it has become completelynonmagnetic.

In this manner, it is possible with the help of relatively low degreesof heating to control magnetic fields which are capable of achieving thedesired effect with a very high degree of certainty. Therefore, therequired heating can be carried out in such a manner that thetemperature-dependent layer is generally heated by athermostaticallycontrolled heat source to the temperature B whichpreferably is slightly above the maximum possible temperature of thesurrounding area. For producing the latent magnetic image it is thenonly necessary to carry out an additional heating of the image-formingportions by less than 5C. These small temperature differences can beapplied even with the help bf copying systems for transparencies as wellas those which project light reflected from an opaque image, althoughparticularly the latter are of relatively low efficiency.

When a strong heat source is available, it is not necessary to carefullycontrol the same, since for producing a difference in the permeabilityby the factor 1,000, it suffices if part of the layer is heated to anytemperature between A and B while other portions of the layer are heatedto a temperature above -C which may be higher than temperature C to anydesired extent, provided that the temperature does not reach the pointat which the original image or for instance the paper backing sheetthereof will be yellowed. 7

It is known from the pertinent literature that in addition to thematerials illustrated in FIG. 1 there exist a great number of othermaterials which are suitable for carrying out the process of the presentinvention. Thus, cobalt-mixed ferrites are known with a steeper rise anda shallower drop of the permeability curve, as well as magnetic metalalloys with Curie points which may be chosen as desired. Furthermore, itwas found experimentally that the temperature curves of materials whichwere not produced for the purpose of having specific Curie points, veryfrequently represent the average values of a mixture from which by meansof magnetic separation after heating to specific temperatures, groups ofmaterial with a correspondingly smaller variation of the temperaturedependency can be obtained.

According to FIG. 2 a temperature dependent, permeable layer 1 isarranged as a magnetic resistance in the field of a magnet pole 4 whichattracts the magnetic ink particles 2 onto a backing sheet 3 which mayconsists, for instance, of paper. In this case, the backing sheet orsupport 5 for the ink is formed of a magnetically neutral material.

In order to stress what is to be essentially shown in this and thefollowing schematic representations, the details of the application ofthe heat image and of the fixing of the copy are not illustratedtherein. In FIGS. 2-9, heating is shown by wavy arrow, induced magnetismby small arrows and permanent magnetism by N or S, whereby the oppositepole or magnetic conductor which is generally required for producing themagnetic field, has not been illustrated. A small minus sign indicatesthat at this point either the permeability has disappeared or, in thecase of the permanent magnetic image, no magnetization has beenproduced. In accordance with these symbols, FIG. 2 shows that at theportions of the intermediate layer which are not touched by the heatrays, due to the there still present permeability, magnetism is inducedwhich is transmitted to the permeable magnetic ink particles whichthereby, at those portions, are attracted to the carrier layer.

According to FIG. 3, the permeable ink particles 2 are firmly held atsuch portions of a highly permeable support which possesses within theworking range of the method a strongly varying permeability, at whichthe high permeability and the magnetism which is induced in this layerby magnetic pole 4 has not disappeared due to heating, or at least hasnot dropped below the value presented by the ink.

According to FIG. 4, magnetic ink 2 possesses a preferably highpermeability and in any event a permeability which within the workingtemperature range of the method is clearly temperature dependent. Bymeans of an external magnetic pole 4 a sufficient magnetism is inducedinto the dye particles which have not been heated above a predeterminedtemperature, which magnetism suffices for attraction of these dyeparticles onto carrying sheet 3.

According to FIG. 5, a layer 1 having a temperature-dependent variablepermeability is located in the magnetizing or demagnetizing field ofexternal magnetic pole 4 which affects a permanently magnetizable layer7. For the purpose of magnetization, pole N may be formed either by astrong permanent magnet or by a direct current coil. Fordemagnetization, the same coil is fed with alternating current. Thecarrier layer 7 is then moved jointly with intermediate layer 1 pastpole 4. Intermediate layer 1, previous thereto has been heated inaccordance with the image which is to be printed or copied, whereby eachportion of permanent magnetic layer 7 passes through the tapered ordecreasing alternating field which is required for demagnetization.

FIG. 6 shows a thin screen or raster 9 which may be formed on amagnetically neutral or generally constant permeable support 8 by aconventional printing process. Raster 9 consists of highly coerciveportions 9a aand temperature dependent permeable portions 9b. If thisraster consists for instance of magnetic pigments such as the one knownas Bayer $11 which is used for producing magnetic recording tape andwhich has a coercive force of 800 oerstedt and a permeability of themagnitude of 10, and of the mixed ferrite Mn .,Zn ,F e 0, which has amaximum permeability of about 2,000, then at temperature B according toFIG. 1, the by far largest portion of the lines of magnetic force 4awill pass through ferrite 9b. However, at temperature C2 at which thepermeability of the ferrite has dropped to the value 1, the lines ofmagnetic force 4b will be passed to a large extent through the rasterportions 9a which consist of Bayer S1 1 which now possess the higherpermeability and will give to these raster portions a permanentmagnetization or, when an alternating field with decreasing amplitude isapplied, will extinguish the previously present premagnetization.

According to FIG. 7, a magnetizable ink layer 10 is applied to amagnetically neutral support 5. Ink layer 10- has been magnetizedaccording to one of the methods described further above in conformancewith an image so as to form a magnetic image. The permanently magneticink portions caused by in duction magnetization of a highly permeablelayer 11 located behind the support for the image copy to be produced,and the magnetized image forming ink portions are attracted in thismanner to the support 3.

According to FIG. 8, a magnetic ink 2 is applied to a support 3 withinterposition of a magnetized sieve which carries a latent magneticimage. At the magnetized portions of the sieve, the preferably highlypermeable ink particles cannot pass the sieve and thus a magnetic screenprint is produced. This effect can also be obtained with a magneticallycontrolled sieve which is formed of a material of temperature-dependentpermeability.

FIG. 9 shows a foil 13 to which ink has been applied by conventionalmeans, for instance an applicator roller which does not contact foil 13,by applying magnetic whiskers or the like so that the dye is appliedonlyat the image forming magnetized portions of foil 3. Themagnetization has been carried out in a known manner with varyingpolarity in order to achieve a better contrast or a sharper delineationof the magnetic fields. The printing from a thus inked foil can becarried out in an offset manner, if desired also with interposition of atransfer cylinder.

In FIG. 10, reference numeral 19 denotes the housing of a simple officecopying device. In this housing is arranged a translucent cylinder 20formed of glass or synthetic material. At its surface, cylinder 20carries a fine screen or raster 20a which consists of groove shapedindentations which may be formed for instance by etching. As shown inmore detail at A and B indentations 20a preferably are of scoop wheelcross section so that on the one hand, they will be capable of carryingalong magnetic powder 22 when passing funnel 21 and, on the other hand,will be capable of throwing off the portion of the powder which byheating has become nonmagnetic and which is not needed for forming theimage, immediately after passing through heating zone a. The applicationof the powder can, if necessary, also be assisted by the properapplication of magnetic fields.

Heating can be carried out in reflex process by means of a heat source18 located in the interior of cylinder 20, or by means of transmittedradiation, utilizing an external heat source 18d. The powder which is tobe heated is located in the immediate vicinity of the original image 23so that a sharply defined heat image will be formed. Due to the factthat any powder which might extend outwardly of the raster indentationsis raked off by means of rubber rake 26, contamination of original image23 cannot take place.

Immediately following heating zones a a magnetic field is arranged whichcovers the entire zone b along which the portions of the powder whichhave been converted by the application of heat are to be thrown off.This magnetic field may be formed, for instance, by a permanent magnetplate 24 located inside cylinder 20. By means of this magnetic field,the portions of the powder which have remained below the conversiontemperature and which correspond to the black portions of original image23 will be held on the surface of cylinder 20. Since glass and syntheticmaterials are very poor heat conductors, a harmful heat conduction inthe short transfer period is not to be expected It is also impossiblethat during this short period of time heat flow can take place withinthe magnetic powder which is located in the small raster indentations.Thus, the sharpness of the image is limited by the dimensions of thevery small raster grooves and the even smaller particle size of thepigment which is chosen as small as possible.

The portion of the magnetic powder which during application of the heatimage has become nonmagnetic as well as nonmagnetic binder constituentsor the like which would interfere with the forming of the copy or theimage, will drop under the influence of gravity into collecting vessel22a. This dropping can be supported, if necessary by mechanical,pneumatic or electrostatic forces. The powder image which remains oncylinder 20 will drop upon reaching the end of the inner magnetic fieldor or permanent magnet plate 24, under the influence of gravity, ontothe support sheet 27 which contacts the lowermost portion of cylinder 20along a printing line. Copy sheet 27, for instance, may be a regularpaper sheet. Since the circumferential speed of cylinder 20 is equal tothe forward speed of copy sheet 27 the transfer of the magnetic powdertakes place without distortion of the image. The exact transfer can besupported if desired by properly arranged magnetic fields.

The fixing of the image formed by the magnetic powder on copy sheet 27can be accomplished for instance with a spray lacquer, or by means of anadhesive layer which has been previously applied to copy sheet 27 or thelike. According to the presently described example, the individualparticles of the magnetic powder which have a Curie point of about 50 C.are coated with a synthetic material which will melt at a temperature ofabout ll C. A source of radiant heat 28 serves for heating the powderimage on carrier sheet 27 to such temperature of 100-l 10 C. so that thepowder image will be molten onto carrier sheet 27. For the movement ofthe original image carrying sheet 23 and of copy sheet 27 guidingrollers 29 are provided which preferably are rotated by means of a jointadjustable motor and which simultaneously are coupled with an interposedsuitable transmission to rotating cylinder 20.

In cases where the magnetic powder is to serve directly and withoutadmixtures as the image forming material, for instance in accordancewith FIGS. 4 and 10, the powder which possesses the magnetic propertiesaccording to FIG. 1 should be ground as fine as possible in order tohave a good adherence to the carrier sheet, for instance a paper surfaceon which the image is to be printed. Very fine grain sizes of themagnetic powder are obtained by wet grinding for between about and 40hours of precominuted ferrite particles. It may be pointed out that theterm mixed ferrite" as used herein does not denote a mixture of severalferrites, but a ferrite which contrary to a simple ferrite contains inaddition to iron not only one metal oxide but several metal oxides, forinstance like the nickel-zinc and manganese-zinc ferrite according toFIG. 1.

In order to produce a magnetic powder which may be adhere'd to the copysheet by heating, as for instance described in connection with FIG. 10,the following method may be followed:

Twentyfive parts by weight of colophony are stirred in liquid conditionwith 100 parts by weight of a ferrite powder such as Ni Zn Fe 0 shown inFIG. 1, and 1 part by weight of channel black or lamp black. Aftercooling, the mass is ground and screened. A deep black magnetic inkpowder is obtained wherein the individual particles are covered by acoating which softens at C. and melts at C. and thereby draws thepigment particles into the surface of the carrier sheet.

It is possible to produce a magnetic printing ink which is suitable foruse in the apparatus of the present invention from the conventionalmaterials of an offset printing ink. Thereby, the magnetic pigment isbound generally in varnishlike binders containing resinous and oilyconstituents. Upon contacting the copy sheet, the constituents of thebinder separate into their component parts. The mineral oil constituentof the printing ink is immediately absorbed by the fiber structure, thefillers or the coating of the thus-printed paper. The resinousconstituents are thereby transformed into an immediately nonsmearablegelatinous form and adhere well to the paper, Known varnish combinationswhich quickly penetrate the paper are polymerized linseed oil and aresinous oil produced from mineral oil, or mineral oil combined withsynthetic resins or rubber. I

Such a magnetic printing ink which contains about between 5075 percentby weight of highly permeable magnetic pig ment particles can betransferred in an inhomogeneous magnetic field which has a maximum fieldstrength of about 500 oerstedt across an air gap of between about 0.5and 1 mm. formed between two rollers. The field strength required forsuch transfer across an air gap will be reduced, in known manner, byabout the square of any reduction of the width of the air gap. It ispossible-to operate with a minimum field strength when transfer rollerand printing form are in direct contact with each other so that directink transfer, due to such contact, would also be possible at thenonmagnetic portions, if in the manner of offset or flat printing suchtransfer at the nonmagnetic portions is prevented by moistening of theprinting form.

Since the highly permeable magnetic pigments do not always possesssufficient color strength, it is frequently advantageous to add theretoa certain percentage of conventional inorganic or organic pigments, forinstance, channel black. This has been done in the example above by theaddition of the multilith printing ink which contains such blackpigments.

It is, of course, also possible to apply in conventional manner, lacquerto the'pigments in order to prevent undesirable spreading in the paper,and the consistency of the ink can be adjusted to the respectiveprinting process in conventional manner by the addition of appropriatediluting or thickening agents.

A layer of variable magnetic resistance corresponding to layer 1 of FIG.2 can be obtained by mixing 50 percent of a pourable polyester resin,such as Leguval made by Bayer, with 45 percent by volume of ferritepowder, such as I500 N 4 made by Siemens, and 5 percent by volume of ahardener (peroxide), and by pouring the mixture onto a proper support,for instance a cylinder. A hard layer is formed thereby having a meanspermeability in cold condition of about p. l5 and in hot condition, i.eabove the Curie point of the ferrite powder, of about p. 1.

In the same manner, however by using 50 percent by volume of Bayer S12powder, it is possible to produce a permanently magnetizable layercorresponding to layer 7 of FIG. 5. The particle size of the powderdepends in both cases on the desired degree of optical resolving powerof the copy layer. Generally, the particle size may average about 10microns.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofmagnetic image forming devices, differing from the types describedabove.

While the invention has been illustrated and described as embodied in amagnetic image-forming device utilizing the temperature variablepermeability of certain materials, it is not intended to be limited tothe details shown, since various modifications and structural changesmay be made without departing in any way from the spirit of the presentinvention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

We claim:

1. A device for forming a copy of an image by utilizing the temperaturedependency of the magnetic permeability of a magnetizable material,comprising, in combination, a cylindrical wall having a substantiallyhorizontal axis, defining an inner cavity and formed at its outersurface with a plurality of closely spaced grooves extending along thelength of the cylindrical wall; means for introducing magnetizablepulverulent material into said grooves at a portionof the outerperiphery of said cylindrical wall which is upstream of the top portionof the rotating wall; means for passing concurrent with the rtation ofsaid cylindrical wall an image carrying sheet along the top portion ofthe same, and a carrier sheet for the image to be formed along thebottom portion of said cylindrical wall so that when said cylindricalwall serves as a printing cylinder, said carrier sheet passes saidcylinder in a printing plane and contacts said cylinder along a printingline formed by the lowermost portion of said cylinder; heating means forheating said image carrying sheet in the area of contact of the samewith the outer surface of said cylinder so that said magnetizablematerial in the grooves located in said area of contact will beselectively heated according to a pattern corresponding to said imagethereby forming in said magnetizable material in said grooves aselective pattern of predetermined magnetic permeability correspondingto said image; magnetic means located .in the cavity of said cylindricalwall adjacent the portion of the cylindrical wall passing from said areatowards said printing line for holding in said grooves only the portionsof said magnetic pulverulent material forming said selective pattern ofpredetermined permeability while allowing the other portions of saidpulverulent material to fall off said cylindrical wall, said magneticmeans terminating adjacent to but spaced from the radial plane of saidcylindrical wall passing through said printing line, whereby at saidprinting line said pulverulent material forming said selective patternwill no longer be subjected to the magnetic force of said magnetic meansand will drop from said grooves onto said carrier sheet forming thereona copy of said image.

2. A device as defined in claim I, wherein said cylindrical wall isformed of translucent material.

3. A device as defined in claim 2, wherein said cylindrical wall isformed of glass.

4. A device as defined in claim 2, wherein said cylindrical wall isformed of synthetic material of low heat conductivity.

5. A device as defined in claim 1, wherein said grooves define ascoop-wheel-shaped configuration at the outer periphery of saidcylindrical wall.

6. A device as defined in claim I, wherein said heating means is locatedoutside said cylindrical wall.

7. A device as defined in claim I, wherein said heating means is locatedwithin said inner cavity by said cylindrical wall.

8. A device as defined in claim 1, wherein said magnetic means includesa curved permanently magnetic plate located inwardly of and closelyadjacent to the portion of the cylindrical wall passing from saidheating means towards said printing line.

9. A device as defined in claim 1, and including fixing means for fixingthe image-forming pulverulent material to said carrier sheet.

10. A device as defined in claim 9, wherein said pulverulent materialincludes a low melting component and said fixing means includes secondheating means for melting said component and thereby fixing thepulverulent material to said carrier sheet.

Patent No. ,786 Dated March 2 1971 lnventofls) Helmut Kaufer et 1 It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

On the cover sheet insert [73] Assignee AGFA Aktiengesellschaft,Leverkusen, Germany Signed and sealed this 25th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patent -'QRM PC4050 [10-69) USCOMM-DC l0!

1. A device for forming a copy of an image by utilizing the temperaturedependency of the magnetic permeability of a magnetizable material,comprising, in combination, a cylindrical wall having a substantiallyhorizontal axis, defining an inner cavity and formed at its outersurface with a plurality of closely spaced grooves extending along thelength of the cylindrical wall; means for introducing magnetizablepulverulent material into said grooves at a portion of the outerperiphery of said cylindrical wall which is upstream of the top portionof the rotating wall; means for passing concurrent with the rotation ofsaid cylindrical wall an image carrying sheet along the top portion ofthe same, and a carrier sheet for the image to be formed along thebottom portion of said cylindrical wall so that when said cylindricalwall serves as a printing cylinder, said carrier sheet passes saidcylinder in a printing plane and contacts said cylinder along a printingline formed by the lowermost portion of said cylinder; heating means forheating said image carrying sheet in the area of contact of the samewith the outer surface of said cylinder so that said magnetizablematerial in the grooves located in said area of contact will beselectively heated according to a pattern corresponding to said imagethereby forming in Said magnetizable material in said grooves aselective pattern of predetermined magnetic permeability correspondingto said image; magnetic means located in the cavity of said cylindricalwall adjacent the portion of the cylindrical wall passing from said areatowards said printing line for holding in said grooves only the portionsof said magnetic pulverulent material forming said selective pattern ofpredetermined permeability while allowing the other portions of saidpulverulent material to fall off said cylindrical wall, said magneticmeans terminating adjacent to but spaced from the radial plane of saidcylindrical wall passing through said printing line, whereby at saidprinting line said pulverulent material forming said selective patternwill no longer be subjected to the magnetic force of said magnetic meansand will drop from said grooves onto said carrier sheet forming thereona copy of said image.
 2. A device as defined in claim 1, wherein saidcylindrical wall is formed of translucent material.
 3. A device asdefined in claim 2, wherein said cylindrical wall is formed of glass. 4.A device as defined in claim 2, wherein said cylindrical wall is formedof synthetic material of low heat conductivity.
 5. A device as definedin claim 1, wherein said grooves define a scoop-wheel-shapedconfiguration at the outer periphery of said cylindrical wall.
 6. Adevice as defined in claim 1, wherein said heating means is locatedoutside said cylindrical wall.
 7. A device as defined in claim 1,wherein said heating means is located within said inner cavity by saidcylindrical wall.
 8. A device as defined in claim 1, wherein saidmagnetic means includes a curved permanently magnetic plate locatedinwardly of and closely adjacent to the portion of the cylindrical wallpassing from said heating means towards said printing line.
 9. A deviceas defined in claim 1, and including fixing means for fixing theimage-forming pulverulent material to said carrier sheet.
 10. A deviceas defined in claim 9, wherein said pulverulent material includes a lowmelting component and said fixing means includes second heating meansfor melting said component and thereby fixing the pulverulent materialto said carrier sheet.